Physiology of Hearing Flashcards
sound is a series of?
of sound waves
in a compressible medium, such as air, what happens to the pressure waves of sound?
the pressure waves cause the molecules of the medium to compress together and pull apart alternately
in an incompressible medium such as water/solids - what happens to the pressure waves of sound?
the pressure wave propagates by direct interaction of the particles
they effectively bump into one another
the waves propagate through?
Through the medium, but the molecules themselves do not change their mean distance from the source
velocity of sound wave in air =
340 m/s
velocity of sound wave in water =
1500 m/s
what is a sound’s frequency?
measured in Hz
it is the number of oscillations per second
what is a sound’s wavelength?
measured in m
it is the distance between points of maximal pressure
what is a sound’s volume?
measured in dB (logarithmic)
it is the difference in pressure between maximal and minimal pressures
what does the pinna do?
it directs sounds into the auditory canal (acoustic meatus)
what does the external ear consist of?
it consists of a vertical portion and a horizontal portion
what does the auditory canal limit?
it limits the frequencies that reach the tympanic membrane (aids with identifying sound direction)
what does the auditory canal contain?
contains glands that secrete cerumen (earwax) and small hairs to trap debris
what does the tympanic membrane do?
it separates the ear canal from the middle ear and is the first part of the sound transducing mechanism
what is the external ear shaped like?
shaped somewhat like a loudspeaker cone (which is an ideal shape for transmitting sound between solids and air)
middle ear cavity extends to?
extends into tympanic bulla
(outcropping of temporal bone)
what is the middle ear connected to and by what?
connective to nasopharynx by auditory tube (Eustachian tube)
auditory ossicles?
malleus
incus
stapes
what does the middle ear allow for?
allows for balance of changes in atmospheric pressure - blockage of the auditory tube can impede hearing and be painful
where is the inner ear embedded?
within the temporal bone
what does the inner ear consist of?
of cochlea
vestibulum
semi-circular canals
what is the stapes attached to - inner ear?
attached to oval window - transduces vibrations of the ossicles to the fluid within the vestibulum and cochlea
what cells does the cochlea contain?
sensory cells
impulses from cochlea transmitted via?
via the cochlear nerve branch of vestibulocoChlear nerve (cranial nerve VIII) to the brain
fluid filled semi-circular canals and vestibule contain what kind of sensors?
sensors on head position and movement
impulses from canals transmitted via? inner ear
via the vestibular nerve branch of vestibulocochlear nerve (cranial nerve VIII) to the brain
when tympanic membrane vibrates, what happens to the waves?
the waves are transmitted via the ossicles onto the oval window
what is the oval window?
it is a membrane held in place by annular ligaments that allow it to bulge into the cochlear
if the ossicle are pulled away, what does it cause?
it causes the changes in the opposite direction
repeated transmission of sound waves occurs along?
along the basilar membrane
movement of the basilar membrane causes?
causes the tectorial membrane of the sensory structure to be displaced
what are not the same along the entire basilar membrane?
amplitudes and sensitivity of the wave are not the same along it
what does frequency discrimination depend on?
depends on the sound frequency
high frequency waves have maximum amplitude near?
near the round window and do not travel far
low frequency waves cause the basilar membrane to vibrate with?
with maximal amplitude near the tip of the cochlea
organ of corti is what type of structure?
a sensory structure
what do travelling waves move?
they move basilar membrane up and down in response to sound stimulation
the tectorial membrane is displaced relative to?
relative to the hair cells
travelling sound waves causes sensory hair bundles to be?
to be bent back and forth at a right angle to the canal
structure of sensory hairs?
they are longer toward the tip of the tectorial membrane - stereocilia
as basilar membrane moves upwards - what happens to hair cells?
hair cells bent towards longest hair
as basilar membrane moves downwards - what happens to hair cells?
hair cells bent towards shortest hair
there are three semi-circular cells why?
one for each dimension
each canal has an ampulla - what is that and what is it containing?
ampulla (enlargement)
containing hair cells in one wall
the hair cell stereocilia project out into a?
into a gelatinous cupula
what happens to the vestibular system when an animal moves its head?
the endolymph within the semi-circular canals lags due to inertia
the lag of the endolymph pushes the what?
pushes the cupula
